One embodiment of the invention relates to a polymer memory device and a method of making it. A content protection system may comprise a multiplicity of such eye characteristic readers and a content protector receiving said at least one characteristic from such readers and controlling the user population’s use of content to be protected based on that at least one characteristic. When the system is operating in a cooling mode, cool air is delivered into the rooms through the lower vents, and air is removed from the rooms through the upper vents. Consequently, the heated cooling medium, after application to the X-ray detector 1, is applied to the X-ray source 2 where a second exchange of heat takes place, so that at the same time the X-ray source 2 is cooled without utilizing an additional cooling circuit.